1. Field of the Invention
This invention relates to motion picture cameras, and more particularly to a motion picture camera with a release device capable of selective control of movement of the shutter for either a normal picture sequence or a single frame shot.
2. Description of the Prior Art
As known in the art, motion picture cameras are normally provided with a control button or trigger which will cause the camera to operate so long as it is pressed. However, it is frequently desired to expose a single frame, rather than a series of frames. Due to the relatively high speed of normal operation, it is virtually impossible to press and release the trigger quickly enough to insure that only one frame will be exposed.
This has led to a modification of the release mechanism with the provision of additional components of particular structure by means of which a single frame shot can be made with ease even by an amateur using a motion picture camera with a release mechanism as such. Further, there has been proposed a wide variety of methods of selective control between a normal motion picture sequence and a single frame shot, as for example, disclosed in U.S. Pat. No. 3,512,881.
This patent provides a release device including first and second stop levers and first and second release buttons. The first stop lever is arranged between the first release button and a notch formed in a portion of a disk member rotatable with the shutter blades as a unit. So long as the first release button is pressed, the stop lever is retained in the disengaged position relative to the notch to perform a normal motion picture sequence, while permitting the second stop lever to remain in an idle position relative to the disk member. For a single frame shot, the second release button may be pressed after the pressing force has been removed from first release button, thereby the first stop lever is taken out of engagement with the disk member and at the same time the second stop lever is brought into cooperation with the disk member so that near the completion of the revolution of the shutter blade the second stop lever engages the disk member at the notch to ensure that only one frame is exposed.
Such a release device is, however, complicated in structure, because of its double system for releasing the camera, that is, with the first release mechanism adapted only for a normal motion picture type of operation and with the second release mechanism only for a single frame shot, and this complexity makes the device body itself so heavy and bulky that it is very difficult to incorporate it in the limited space available within the housing of a small size motion picture camera of compact structure. Further, such a release mechanism arrangement does not permit sufficiently high accurate and reliable movements of the individual stop levers relative to each other and to the disk member, and is liable to lead to possible damage to the device. Furthermore, another disadvantage is that, because of the provision of two release buttons which are operated independently of each other, namely, the first release button for the motion picture type of operation and the second release button for the single frame shot, the depression of the wrong release button from that to which the photographer intended to depress may take place with resultant incorrect operation, such that though the photographer intends to photograph a motion picture sequence, a single frame shot will result, or vice versa.
Besides the aforesaid type of release device, there is also known another type of release device including a single stop lever arranged so that near the completion of one revolution of a shutter blade the stop lever engages the shutter blade to ensure that only one frame will be exposed despite the fact that a single release button remains depressed, thus omitting the second stop lever and the second release button, as disclosed in U.S. Pat. No. 3,178,721.
This patent is concerned with a control mechanism for a motion picture camera with a shutter blade carrying a fixed pin. A single stop lever is provided upon engagement with the pin to stop the shutter blade in the exposure aperture closed position. This stop lever is movable in only one plane as it is releasably latched to a pivotal member a by latching member provided thereon which pivotal member is arranged to be movable in only one plane perpendicular to the plane of rotation of the shutter blade in response to the actuation of a single release button. The stop lever and pivotal member operate as a unit so long as a selector is set in the first operating position for a normal motion picture type of operation, where the cam surface of the latching member is positioned out of the path of movement of the pin, when the release button is depressed. Once the force is released from the release button, the pin engages the cam surface at a time near the completion of one revolution of the shutter blade to cause unlatching of the stop lever which in turn causes movement of the stop lever into the path of rotation of the pin under the action of its own resilience. For a single frame shot, the selector may be set from the first operating position to the second operating position where pivotal movement of the pivotal member is limited to a smaller extent than that when set to the first operating position, in more detail, to such an extent as that sufficient to release the pin from engagement with the stop lever but insufficient to move the cam surface of the latching member entirely clear of the path of rotation of the pin. With this arrangement, therefore, when the release button is depressed, the pivotal member together with the stop lever still latched thereto move as a unit to a position where the acting edge of the stop lever alone is displaced out of the path of rotation of the shutter pin to start the camera. When the shutter blade comes to a point just before the completion of one revolution, the pin engages the cam surface of the latching member and moves the latching member out of latching engagement with the stop lever. Under the action of its own resilience, the stop lever pivotally returns to the engaged position with the aforesaid pin, and hence the shutter blade is stopped at the time one revolution of the shutter blade has been completed in order to insure that only one frame is exposed.
As is understandable from the above, the release device constituting part of the control mechanism of U.S. Pat. No. 3,178,721 has a higher possibility of reducing the dimensions of the device body itself than that of U.S. Pat. No. 3,512,881, namely owing to the omission of the second release button and second stop lever which function as essential components in the latter device, thereby giving an additional advantage of avoiding incorrect operation of the camera which may be encountered when the exposure mode is changed between a normal motion picture sequence and a single frame shot.
On the other hand, however, many difficulties have been introduced to the construction of a control mechanism as such. For example, in order to impart the function of performing a single frame shot into the control mechanism, the shutter control means has to be divided into two members movable relative to each other, namely, the pivotal member and the stop lever, and arranged to necessitate a latching member by means of which the two members are coated as a unit when the camera is set in the position for the normal motion picture sequence. This latching member must be so dimensioned that when the camera is set to the position for a single frame shot the aforesaid latching be released just before the completion of one revolution of the shutter blade to permit effective operation of the stop lever alone, independently of other components. Thus the complete release device is a very complicated structure. In addition, these and other moving parts must be manufactured to close tolerances, or otherwise the selective control of the shutter between positions for a normal motion picture type of operation and for a single frame shot would be made impossible. For example, the amount of movement of the pivotal member must be accurately adjusted by means of a selector lever so that when in the normal motion picture position, the acting end of the stop lever and the cam surface of the latching member are movable for a sufficient distance from the path of rotation of the shutter pin, while when in the single frame position the acting end of the stop lever only is moved away from the path of rotation of the shutter pin, but the cam surface of the latching member is retained in the path. In view of such close tolerances, complicated construction and the necessity of fine adjustment of the relative positions of various components, the reliability and repeatability of the camera is greatly impaired. Further, in assembling a complete release device as incorporated in the camera body, from these components it is practically very difficult to effect sufficiently fine adjustment of these components in position in order for the camera to operate satisfactorily.
As the control mechanism of U.S. Pat. No. 3,178,721 operates in a very elaborate manner, and therefore results in a relatively complicated construction for controlling operation of the shutter, much is left to be desired. In producing economically a good release device for a motion picture camera of the type capable of selective control of the shutter for a normal motion picture type of operation and for a single frame shot, there remain many problems yet to be solved. Such problems become serious when the camera is of small and compact type.